• Applied Biological Chemistry
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• v.43 no.3
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• pp.169-173
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• 2000

For the development of enzyme detergent capable of effectively washing at low temperature, a bacterium producing alkaline protease was isolated from soil samples, and properties of the enzyme were investigated. The selected strain was Gram negative, rod shape$(0.6{\sim}0.7{\times}1.3{\sim}2.6\;{\mu}m\;in\;size)$ and motile. It had the degradation activity of aesculin, gelatin and casein, and was catalase-positive. The cell wall components was meso-DAP, and G+C mole contents was 43.3%. From these results, the strain was identified as Acinetobacter sp. KN-27. The activity of alkaline protease by this strain peaked with 3,300 D.U/mL after 36 hours in the liquid culture at $40^{\circ}C$. The optimal pH and temperature of the enzyme were pH 9 and $60^{\circ}C$, respectively. Alkaline protease produced by Acinetobacter sp. KN-27 has shown two active bands on the electrophoresis of native gel.

• Annals of Laboratory Medicine
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• v.38 no.6
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• pp.545-554
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• 2018

Background: The increasing morbidity and mortality rates associated with Acinetobacter baumannii are due to the emergence of drug resistance and the limited treatment options. We compared characteristics of colistin-resistant Acinetobacter baumannii (CR-AB) clinical isolates recovered from patients with and without prior colistin treatment. We assessed whether prior colistin treatment affects the resistance mechanism of CR-AB isolates, mortality rates, and clinical characteristics. Additionally, a proper method for identifying CR-AB was determined. Methods: We collected 36 non-duplicate CR-AB clinical isolates resistant to colistin. Antimicrobial susceptibility testing, Sanger sequencing analysis, molecular typing, lipid A structure analysis, and in vitro synergy testing were performed. Eleven colistin-susceptible AB isolates were used as controls. Results: Despite no differences in clinical characteristics between patients with and without prior colistin treatment, resistance-causing genetic mutations were more frequent in isolates from colistin-treated patients. Distinct mutations were overlooked via the Sanger sequencing method, perhaps because of a masking effect by the colistin-susceptible AB subpopulation of CR-AB isolates lacking genetic mutations. However, modified lipid A analysis revealed colistin resistance peaks, despite the population heterogeneity, and peak levels were significantly different between the groups. Conclusions: Although prior colistin use did not induce clinical or susceptibility differences, we demonstrated that identification of CR-AB by sequencing is insufficient. We propose that population heterogeneity has a masking effect, especially in colistin non-treated patients; therefore, accurate testing methods reflecting physiological alterations of the bacteria, such as phosphoethanolamine-modified lipid A identification by matrix-assisted laser desorption ionization-time of flight, should be employed.

• Korean Journal of Clinical Laboratory Science
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• v.50 no.4
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• pp.431-437
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• 2018

Acinetobacter baumannii is categorized as a red alert pathogen that is increasingly associated with a high mortality rate in infected patients because of its resistance to extensive antibiotics. This study evaluated the antibacterial activities of some essential oils (tee tree, rosemary, and lavender oils) against 18 clinical isolates of multidrug-resistant A. baumannii (MRAB). The carbapenemase screening Hodge test showed that all 20 strains of A. baumannii were resistant to imipenem. The identification of multidrug-resistant microbes was carried out using the VITEK system. The antimicrobial activity of essential oils was tested by a disk diffusion method against MRAB. In the disk diffusion method, tea tree showed the largest increase in inhibition size compared to lavender oil, and rosemary had no antibacterial effect. These results proved the antimicrobial effect of multidrug resistance A. baumannii. Tee tree oil would be a useful alternative natural product for the treatment and prevention of most common human pathogens and MRAB infections. This is expected to be used as an antimicrobial agent, such as hand disinfectant using natural essential oil in the future.

• IMMUNE NETWORK
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• v.20 no.3
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• pp.25.1-25.13
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• 2020

Acinetobacter baumannii is known for its multidrug antibiotic resistance. New approaches to treating drug-resistant bacterial infections are urgently required. Cathelicidin-related antimicrobial peptide (CRAMP) is a murine antimicrobial peptide that exerts diverse immune functions, including both direct bacterial cell killing and immunomodulatory effects. In this study, we sought to identify the role of CRAMP in the host immune response to multidrug-resistant Acinetobacter baumannii. Wild-type (WT) and CRAMP knockout mice were infected intranasally with the bacteria. CRAMP^-/- mice exhibited increased bacterial colony-forming units (CFUs) in bronchoalveolar lavage (BAL) fluid after A. baumannii infection compared to WT mice. The loss of CRAMP expression resulted in a significant decrease in the recruitment of immune cells, primarily neutrophils. The levels of IL-6 and CXCL1 were lower, whereas the levels of IL-10 were significantly higher in the BAL fluid of CRAMP^-/- mice compared to WT mice 1 day after infection. In an in vitro assay using thioglycollate-induced peritoneal neutrophils, the ability of bacterial phagocytosis and killing was impaired in CRAMP^-/- neutrophils compared to the WT cells. CRAMP was also essential for the production of cytokines and chemokines in response to A. baumannii in neutrophils. In addition, the A. baumannii-induced inhibitor of κB-α degradation and phosphorylation of p38 MAPK were impaired in CRAMP^-/- neutrophils, whereas ERK and JNK phosphorylation was upregulated. Our results indicate that CRAMP plays an important role in the host defense against pulmonary infection with A. baumannii by promoting the antibacterial activity of neutrophils and regulating the innate immune responses.

• Genomics & Informatics
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• v.13 no.1
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• pp.2-6
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• 2015

Pathogenic bacteria survive in iron-limited host environments by using several iron acquisition mechanisms. Acinetobacter baumannii, causing serious infections in compromised patients, produces an iron-chelating molecule, called acinetobactin, which is composed of equimolar quantities of 2,3-dihydroxybenzoic acid (DHBA), L-threonine, and N-hydroxyhistamine, to compete with host cells for iron. Genes that are involved in the production and transport of acinetobactin are clustered within the genome of A. baumannii. A recent study showed that entA, located outside of the acinetobactin gene cluster, plays important roles in the biosynthesis of the acinetobactin precursor DHBA and in bacterial pathogenesis. Therefore, understanding the genes that are associated with the biosynthesis and transport of acinetobactin in the bacterial genome is required. This review is intended to provide a general overview of the genes in the genome of A. baumannii that are required for acinetobactin biosynthesis and transport.

• BMB Reports
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• v.30 no.2
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• pp.132-137
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• 1997

In order to compare molecular structure, malonate decarboxylases from Acinetobacter calcoaceticus, Pseudomonas fluorescens, and Pseudomonas putida aerobically grown on malonate, were purified by the method employing streptomycin sulfate treatment, chromatography with PBE 94 and ${\omega}-aminohexyl$ agarose. Molecular masses were estimated to be 185, 200, and 200 kDa, respectively. All malonate decarboxylases were multimeric enzymes consisting of four different subunits, $2{\alpha},\;1{\beta},\;1{\gamma},\;and\;1{\delta}$. The molecular masses of the Pseudomonas enzyme subunits were $65({\alpha})$, $33({\beta})$, $30({\gamma})$, and $11kDa({\delta})$; which are very similar to those, $65({\alpha})$, $32({\beta})$, $25({\gamma})$, and $11kDa({\delta})$ of Acinetobacter enzyme. The ${\delta}-subunit$ of the active form of the enzymes was acetylated. The acetyl group may form a thioester bond with the thiol group of the prosthetic group covalently linked to the enzyme. It suggests that such molecular organization is common in all malonate decarboxylases.

• BMB Reports
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• v.34 no.2
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• pp.172-175
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• 2001

Catechol 1,2-dioxygenase $I_1$ ($CDI_1$) is the first enzyme of the $\beta$-ketoadipate pathway in Acinetobacter lowffii K24. $CDI_1$ has two cysteines (155, 202) and its enzyme activity is inhibited by the cysteine inhibitor, $AgNO_3$. Two mutants, $CDI_1$ C155V and $CDI_1$ C202V, were obtained by site-directed mutagenesis. The two mutants were overexpressed and the mutated amino acid residues (Cys$\rightarrow$Val) were characterized by peptide mapping and amino acid sequencing. Interestingly, $CDI_1$ C155V was inhibited by $AgNO_3$, whereas $CDI_1$ C202V was not inhibited. This suggests that $Cys^{202}$ is the sole inhibition site by $AgNO_3$ and is close to the active site of the enzyme. However, the results of the biochemical assay of mutated $CDI_1s$ suggest that the two cysteines are not directly involved in the activity of the catechol 1,2-dioxygenase of $CDI_1$.

• BMB Reports
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• v.34 no.3
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• pp.230-236
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• 2001

dTDP-rhamnose is synthesized from dTTP and glucose-1-phosphate by four enzymatic steps in the gram-negative bacteria. By using a homologous PCR product, a gene cluster encoding four genes (rfbA, rfbB, rfbC, rfbD) involved in L-rhamnose biosynthesis by Acinetobacter calcoaceticus was isolated and sequenced. The four genes were clustered on the biosynthetic operon in the order of rfbB, D, A, C. A gene, rfbA, encoding glucose-l-phosphate thymidylyltransferase (RfbA), was cloned from A. calcoaceticus pathogenic and encapsulated in the gram-negative bacterium. This enzyme catalyzes the formation of dTDP-D-glucose From $\alpha$-D-glucose-1-phosphate and dTTP.RfbA was amplified by PCR and inserted into the $T_7$ expression system. The activity of RfbA was determined by the capillary electrophoresis. The $K_m$ values for dTTP and $\alpha$-D-glucose-1-phosphate were calculated to be 1.27 mM and 0.80 mM, respectively by using the Line-Weaver Burk plot. RfbA is inactivated by diethylpyrocarbonate.

• The Plant Pathology Journal
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• v.20 no.4
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• pp.293-296
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• 2004

During the screening of antiviral substances having inhibitory effects on Tobacco mosaic virus (TMV) infection on tobacco plants, we found a bacterial isolate KTB3, and identified it as Acinetobacter sp. which strongly inhibited the infection of TMV When the culture filtrate from KTB3 was applied on the upper surface of the Xanthi-nc tobacco leaves at the same time, or 24 hours before TMV inoculation, almost complete inhibition was achieved. Likewise, 86% inhibition was achieved, when the culture filtrate was applied on the underside of the leaves. In field trials, transmission of TMV from diseased seedlings to healthy ones during transplanting work was reduced by 92%, when the culture filtrate was sprayed onto the tobacco seedlings, cv. NC82, 24 hours before transplanting. No toxic effect was observed on the tobacco plants. Antiviral substance from the culture filtrate was purified by ethanol precipitation, dialysis, DEAE-cellulose, and Sephadex G75 gel column chromatography. The partially purified active material which showed positive color reaction to sugar and protein inhibited TMV infection by 60% at 1 ${\mu}$g/ml.

• Microbiology and Biotechnology Letters
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• v.25 no.5
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• pp.520-526
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• 1997

Bacterial strains which degrade Arabian Light crude oil were isolated by enrichment culture from oil-spilled soil. The strain A54 was finally selected after testing emulsifying activity and oil conversion rate. Strain A54 was identified as a Acinetobacter sp. based on the morphological, biochemical and physiological characteristics. It appears to be highly specialized for growth on Arabian Light crude oil in minimal salts medium since it showed preference for oil or degradation products as substrates for growth. It was found that it could grow on at least fifteen different hydrocarbons. The optimum cultural and environmental conditions were as follows; 25$\circ$C for temperature, 7,5 for pH, 2.0% for NaCl concentration and 2.0% for crude oil concentration. Additionally, the optimal concentration of NH$_{4}$NO$_{3}$, and K$_{2}$HPO$_{4}$, were 12.5 mM and 0.057 mM, respectively. Cell growth and emulsifying activity as a function of time were also determined. Crude oil degradation and the reduction of product peaks were identified by the analysis of remnant oil by gas chromatography. Approximately 63% of crude oil were converted into a form no longer extractable by mixed organic solvents.